The invention relates to a rear view mirror for a motor vehicle having a mirror element, in the mirror surface of which the driver may observe the traffic behind him. The invention further relates to various methods of controlling a rear view mirror according to the invention.
Rear view mirrors of the type described are used in vehicles of all kinds, such as e.g. passenger cars, trucks and motorcycles, to enable the driver to observe the traffic behind him. Here, there is fundamentally a distinction between inside rear view mirrors, which are disposed in the interior of a vehicle, and outside rear view mirrors which are disposed outside of the vehicle. As the mirror element of the known rear view mirrors, glass mirror elements are mainly used.
The drawback of the known mirror glasses is that the available reflective surface is permanently defined by the style of construction and cannot be varied. Thus, mirror glasses both with a flat and with a convex reflective surface are known. A switchover between a flat and convex reflective surface is however not possible with the conventional mirror glasses so that, for example, the enlargement ratio of an imaged reflection detail is defined invariably by the curvature of the mirror glass. Nor is it possible to present different reflection details which are adjustable by the driver.
The object of the present invention is to provide a rear view mirror, the reflective surface of which may be variably adjusted to the needs of the driver.
The invention is based on the fundamental idea that the reflective surface of the rear view mirror is not formed by one mirror element but is composed of a plurality of, but at least two, component mirrors. These component mirrors are pivotally mounted on a base plate and each component mirror may be displaced relative to the base plate by activating a drive unit associated with the respective component mirror. Independent adjustment of the angle of reflection of each individual component mirror is therefore possible. By virtue of the coordinated adjustment of the various angles of reflection of the component mirrors, reflective surfaces of differing characteristics may be achieved. By virtue of the arrangement of a plurality of component mirrors in the reflective surface, the surface as a whole appears homogeneously reflective. When only a few component mirrors are used, each component mirror may be directed independently of one another towards a different reflection detail. Depending on the actual driving situation, e.g. driving on a freeway or maneuvring into a parking space, the reflective surface may be varied and adapted in each case by altering the setting of the component mirrors. A rear view mirror according to the invention may be used both as an outside and as an inside rear view mirror.
It is particularly advantageous when the component mirrors are adjustable in a coordinated manner by means of a central control unit. The control unit in said case translates the control commands of the driver, e.g. the adjustment of a reflective surface with convex mirror characteristics, into corresponding control commands for adjustment of the various component mirrors.
The component mirrors may in principle be mounted in any desired manner on the base plate. It is particularly advantageous when the component mirrors are connected by a resilient connecting element to the base plate. The resilient connecting element by means of its load-free basic alignment defines the normal position of each component mirror. Thus, for example, a flat reflective surface may be formed when all of the component mirrors are in the normal position. By virtue of the resilient properties of the connecting element, each component mirror after deflection by the associated drive unit is restored resiliently into the normal position so that, e.g. in the event of failure of one or more drive devices, a basic function of the rear view mirror is maintained.
The component mirrors may in principle be of any desired design. Particularly easy manufacture is achieved when the component mirrors are manufactured using thin-film technology. Corresponding components are already known from prior art for use in optoelectronics and are usually known as digital micromirror devices (DMDs). Such DMD chips are available from, for example, Texas Instruments, which use over 500000 microscopic mirrors on a chip to reflect images on a screen. Such DMD chips comprise a plurality of miniaturized component mirrors, which may be displaced by means of drive units integrated on the chip. Such DMD chips may, in order to realize a rear view mirror according to the invention, be integrated in the mirror surface of the rear view mirror. In such case, according to the invention it is immaterial whether the entire mirror surface or only a part of it is formed by DMD chips. Depending on the size of the available DMD chips, a plurality of DMD chips may also be arranged adjacent to one another to realize the mirror surface.
In order to adapt the mirror element 2 composed of component mirrors 3 to a specific mirror surface contour, the component mirrors disposed in the region of the edge of the mirror element may be partially and/or completely covered by another component, e.g. the edge of the mirror housing.
Through use of the component mirrors according to the invention it is conceivable that mirror-adjusting mechanisms suitable for adjusting the rear view mirror to adapt it to the needs of the driver and known from prior art will no longer be required because the adjustment is effected by means of the adjustment according to the invention of the component mirrors. And as a result of the use of DMD chips a substantial amount of weight and space is saved.
A further advantage arises when the component mirrors may be displaced at high frequency between a reflector position and an anti-dazzle position, such as is possible for example with DMD chips. In the reflector position a specific reflection detail is imaged in the mirror surface of the component mirror, whereas in the anti-dazzle position there is no visible imaging. By switching back and forth between the two positions at a suitably high frequency an anti-dazzle effect may be achieved so that, for example, the light of the headlamps of vehicles following behind is imaged only with a diminished light intensity. Other anti-dazzle devices, such as are occasionally used with conventional mirrors, are therefore no longer required. The anti-dazzle factor may be adjusted by varying the switching rate.
For control of the component mirrors according to the invention, it is further advantageous when at least some of the component mirrors are adjustable to a separate field of vision. Thus, for example, when driving on a freeway the blind angle at the driver""s side may be included in the field of vision. It is also conceivable, when reversing, for the component mirrors at the front passenger side to be adjusted in the manner of a parking aid so that the curbstone at the front passenger side comes into the field of vision.
As each individual component mirror may be controlled individually, it is also possible for the component mirrors in dependence upon their position on the base plate to be adjusted at different angles such that the mirror surface as a whole acts like a Fresnel lens. The component mirrors in said case form, for example, concentric circles or segments of a circle and the component mirrors of one circle or segment of a circle have the same setting angle and the setting angle of the various circles or segments of a circle varies in dependence upon the distance from the center of the circle. By controlling the component mirrors in such a way as to act like a Fresnel lens, enlargements or reductions of a reflection detail may be presented with an appropriate enlargement ratio in the reflective surface.
Control of the component mirrors is preferably effected by means of suitably programmable control software.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated.